Simultaneous statistical suspension copolymerization of vinyl chloride with butyl acrylate and grafting on poly(butyl acrylate)

Abstract

An intrinsically softened poly(vinyl chloride–butyl acrylate) was prepared by the suspension statistical polymerization of vinyl chloride (VC) with butyl acrylate (BA) using oil-soluble initiators, dispersants, and a buffer agent, at the temperature 59 ± 1°C (procedure A). The polymer obtained was sufficiently soft and elastic, depending on the ratio of VC and BA; however, the polymer was hard to process. It stuck to metal parts of an assembly line. The properties of the polymer were slightly modified, mainly by addition of crosslinking agents, and improved treatability was obtained in this way. Acceptable treatability was obtained only after preplastification. Similar features were exhibited by a polymer prepared by grafting of a fine dispersion of polybutyl acrylate (PBA) with VC (procedure B). The dispersion of PBA was prepared separately via the emulsion polymerization of BA at 75 ± 1°C (the weight ratio H2O : BA = 2; a mixture of sodium alkane sulfonates 0.95 w/w % and K2S2O8 0.4 w/w % with respect to BA). An intrinsically softened polymer with elasticity derived from the amount of incorporated BA was obtained; unfortunately, as with case A, the polymer was difficult to work up, and preplastification was necessary. The best procedure for the preparation of intrinsically softened poly(vinyl chloride–butyl acrylate) proved to be simultaneous statistical copolymerization of VC and BA, and grafting on PBA (procedure C). The principle consists of gradual addition of VC and BA to the fine dispersion of PBA. A shape stable, aesthetic looking, and well readily processible material was obtained. The ductility of foils prepared from the polymer increases with the increasing amount of BA, while the temperature stability, hardness, and mechanical strength decrease. A hypothesis expressing the morphology of a polymer with good properties has been proposed. Significantly different values of copolymerization parameters of BA (approx. 5) and VC (approx. 0.1) are responsible for irregularities in a copolymer when all amounts of monomers are added at the start of the reaction. The rate of addition of monomers to the polymeric reaction mixture ought to be at such a rate as to allow the formation of relatively regular alternated chains of homopolymers and copolymers of BA and VC that start to grow mainly from the core represented by PBA chains. At the end of copolymerization, an excess of VC is useful for making a PVC hydrophobic cover of particles, and, in consequence, low stickiness to metal surfaces. This may be used for the description of a good polymer, as well as to account for bad properties of other copolymers of BA and VC. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 649–656, 1998